Consolidation Group Change - Elimination of a Subgroup

We are faced with the following scenario - several intermediate parents/groups were dissolved and we would like to remove them from the hierarchy. The hierarchy looks like this:

CG1 (top node)

- CU1

CG2 (intermediate group to be removed)

- CU2 (owneed 100% by CU1; intermediate parent dissolved)

CG3

- CU3 (owned 100% by CU2)

CU3.1 owned by CU3

CU3.2.owned by CU3

etc.

The CU2 has been dissolved and the trial balance completely eliminated. CU1 has an investment in CU2 and CU2 has an investment in CU3. CU2 has been divested from CU1 and CU3 has been transfered from CU2 to CU1. As of the start of the next year, CG2 is removed from the hierarchy. However, at that point, the opening balance for CG1 no longer matches the closing balance for the year before. This is because documents posted at CG2 and reversed at CG1 used to balance to zero in the previous year but in the year following the change, CG2 is no longer part of the hierarchy and the balances created by these documents are no longer zero at CG1 level. Any suggestiongs on how to best handle this will be very welcome.

Please note that I did search all the previous posts and the posts I found were all dealing with the transfer of a cons unit from one group to another. I could not find a post that talks about moving the entire group. Hence, I decided to start a new discussion.